Fundamentally speaking, are humans good or bad? It's a question that has repeatedly been asked throughout humanity. For thousands of years, philosophers have debated whether we have a basically good nature that is corrupted by society, or a basically bad nature that is kept in check by society. Psychology has uncovered some evidence which might give the old debate a twist.

One way of asking about our most fundamental characteristics is to look at babies. Babies' minds are a wonderful showcase for human nature. Babies are humans with the absolute minimum of cultural influence – they don't have many friends, have never been to school and haven't read any books. They can't even control their own bowels, let alone speak the language, so their minds are as close to innocent as a human mind can get.

The only problem is that the lack of language makes it tricky to gauge their opinions. Normally we ask people to take part in experiments, giving them instructions or asking them to answer questions, both of which require language. Babies may be cuter to work with, but they are not known for their obedience. What's a curious psychologist to do?

Fortunately, you don't necessarily have to speak to reveal your opinions. Babies will reach for things they want or like, and they will tend to look longer at things that surprise them. Ingenious experiments carried out at Yale University in the US used these measures to look at babies' minds. Their results suggest that even the youngest humans have a sense of right and wrong, and, furthermore, an instinct to prefer good over evil.

How could the experiments tell this? Imagine you are a baby. Since you have a short attention span, the experiment will be shorter and loads more fun than most psychology experiments. It was basically a kind of puppet show; the stage a scene featuring a bright green hill, and the puppets were cut-out shapes with stick on wobbly eyes; a triangle, a square and a circle, each in their own bright colours. What happened next was a short play, as one of the shapes tried to climb the hill, struggling up and falling back down again. Next, the other two shapes got involved, with either one helping the climber up the hill, by pushing up from behind, or the other hindering the climber, by pushing back from above.

Already something amazing, psychologically, is going on here. All humans are able to interpret the events in the play in terms of the story I’ve described. The puppets are just shapes. They don't make human sounds or display human emotions. They just move about, and yet everyone reads these movements as purposeful, and revealing of their characters. You can argue that this “mind reading”, even in infants, shows that it is part of our human nature to believe in other minds.

Great expectations

What happened next tells us even more about human nature. After the show, infants were given the choice of reaching for either the helping or the hindering shape, and it turned out they were much more likely to reach for the helper. This can be explained if they are reading the events of the show in terms of motivations – the shapes aren't just moving at random, but they showed to the infant that the shape pushing uphill "wants" to help out (and so is nice) and the shape pushing downhill "wants" to cause problems (and so is nasty).

The researchers used an encore to confirm these results. Infants saw a second scene in which the climber shape made a choice to move towards either the helper shape or the hinderer shape. The time infants spent looking in each of the two cases revealed what they thought of the outcome. If the climber moved towards the hinderer the infants looked significantly longer than if the climber moved towards the helper. This makes sense if the infants were surprised when the climber approached the hinderer. Moving towards the helper shape would be the happy ending, and obviously it was what the infant expected. If the climber moved towards the hinderer it was a surprise, as much as you or I would be surprised if we saw someone give a hug to a man who had just knocked him over.

The way to make sense of this result is if infants, with their pre-cultural brains had expectations about how people should act. Not only do they interpret the movement of the shapes as resulting from motivations, but they prefer helping motivations over hindering ones.

This doesn't settle the debate over human nature. A cynic would say that it just shows that infants are self-interested and expect others to be the same way. At a minimum though, it shows that tightly bound into the nature of our developing minds is the ability to make sense of the world in terms of motivations, and a basic instinct to prefer friendly intentions over malicious ones. It is on this foundation that adult morality is built.

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